Under certain conditions galvanic cells may generate large quantities of gas. As these cells are sealed in order to prevent loss of electrolyte, such gas generation may result in the formation of high pressures within such cells. If such high pressures are not vented, cell leakage, bulging and/or rupture may occur.
In the past many approaches have been adopted for releasing the internal pressure which may build up in galvanic cells. In general, it is preferable to employ resealable venting means in order to avoid drying out of the electrolyte and to prevent the ingress of oxygen from the atmosphere which can cause wasteful corrosion of the anode. One significant drawback encountered with several of the prior art resealable vents has been that they require the addition of several or more parts in the dry cell and thus can greatly increase the cost of manufacture. Additionally, these prior art approaches frequently require that these additional parts must be accurately positioned during cell assembly if reliable and reproducible results are to be obtained.
Among the resealable venting means developed in the prior art to overcome the above-described drawbacks are the dry cell constructions disclosed in U.S. Pat. Nos. 3,802,923 and 4,146,681. U.S. Pat. No. 3,802,923 discloses a "rim vent" seal closure for the open end of a cell comprising a cover including an annular depending flange which has a circumferential notch for engaging the inwardly turned peripheral edge of the cell and a resilient sealing lip which resides on the curled over top portion of the container. U.S. Pat. No. 4,146,681 discloses an improved version of such cover wherein an annular recess is located in the cover, which recess extends below the level of the notch, and a locking collar is inserted into such recess.
Although the seal closures of the above patents function admirably, such seals require a large crimp radius. As a result the cell volume is not fully utilized and cathode mix height is not maximized.
It is therefore an object of this invention to provide a resealable vent closure for use in a galvanic dry cell.
Another object of this invention is to provide a resealable vent closure which requires a minimum number of parts and which is therefore easy to assemble and inexpensive to manufacture.
An additional object of this invention is to provide a resealable vent closure which will permit a maximum amount of active material to be placed inside the cell container.
Still another object of this invention is to provide a method for the production of galvanic cells which possess a resealable vent closure.
The foregoing and additional objects will become more fully apparent from the following description and the accompanying drawing.